vidjil_browser.rb: Hover after clicking

When clicking it seems that the mouse isn't necessarily over the menu. Thus it
will open and close just after because the mouse isn't over the menu.

Fix #3987

browser/test/functional/vidjil_browser.rb

@@ -184,9 +184,7 @@ class VidjilBrowser < Watir::Browser
   end
 
   def menu_item_export(id, extra = {})
-    menu = menu_import_export
-    menu.click
-    return menu.a(extra.merge(:id => id))
+    return menu_item(id, extra)
   end
 
   def menu_item_export_fasta(extra = {})
@@ -206,6 +204,7 @@ class VidjilBrowser < Watir::Browser
     end
     if parent.tag_name != "body"
       parent.click
+      parent.hover
     end
     return item
   end